A virus definition update published by Microsoft earlier this week breaks down Security Essentials and Windows Defender on Windows 7 and Windows 8.1, based on reports.

By the looks of products, the culprit may be the virus definition update to version 1.289.1521.0, with several users confirming that whenever installing this release, real-time protection is turned off and also the security apps issue warnings that malware definitions are out of date.

Managing a manual scan on the affected computers fails with error 0x800106ba because of the botched update, so neither Microsoft Security Essentials nor Windows Defender can detect and take away malware on the Windows device.

According to Mary Jo Foley of ZDNet, Windows 10 isn't affected, and Windows Defender is running correctly on this version of the operating system.

"Issue already fixed"

In a statement provided earlier today, Microsoft acknowledged the issue and said a brand new update was pushed to devices in order to correct it. However, the software giant claimed only Windows 7 and Windows Server 2008 were affected, even though there will also be reports that Windows 8.1 devices no longer benefit from native anti-malware protection either.

"We've resolved this problem, which has been restricted to Windows 7 and Windows Server 2008," a company spokesperson was quoted as saying by the cited source.

The software giant hasn't specifically mentioned the virus definition update that corrects the issue, but according to this official listing, the brand new version is 1.289.1588.0. In other words, this is actually the virus definition update that you must install in order to restore the full functionality of Security Essentials and Windows Defender on Windows 7 and 8.1.

Windows Defender is provided as built-in anti-malware protection on Windows 8.1 and Windows 10, while Microsoft Security Essentials must be manually placed on Windows 7 devices. However, both are provided with regular virus definition updates and offer users real-time protection and a manual scanning engine.